Attribute Value Reordering for Efficient Hybrid OLAP

Kaser, Owen et Lemire, Daniel (2006). « Attribute Value Reordering for Efficient Hybrid OLAP ». Information Systems, 176(16), pp. 2279-2438.

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Résumé

The normalization of a data cube is the ordering of the attribute values. For large multidimensional arrays where dense and sparse chunks are stored differently, proper normalization can lead to improved storage efficiency. We show that it is NP-hard to compute an optimal normalization even for 1x3 chunks, although we find an exact algorithm for 1x2 chunks. When dimensions are nearly statistically independent, we show that dimension-wise attribute frequency sorting is an optimal normalization and takes time O(d n log(n)) for data cubes of size n^d. When dimensions are not independent, we propose and evaluate several heuristics. The hybrid OLAP (HOLAP) storage mechanism is already 19%-30% more efficient than ROLAP, but normalization can improve it further by 9%-13% for a total gain of 29%-44% over ROLAP.

Type:	Article de revue scientifique
Mots-clés ou Sujets:	Multidimensional Databases, Data Cubes, Multidimensional Binary Arrays, OLAP, MOLAP, HOLAP, Normalization, Chunking
Unité d'appartenance:	Télé-université > UER Science et Technologie
Déposé par:	Daniel Lemire
Date de dépôt:	05 juin 2007
Dernière modification:	01 nov. 2014 02:03
Adresse URL :	http://archipel.uqam.ca/id/eprint/313

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